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Toxicity to microorganisms

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Endpoint:
activated sludge respiration inhibition testing
Remarks:
and other
Type of information:
other: review
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The EU RAR summarises and reviews the available data on the toxicity of fluoride to aquatic microorganisms
Qualifier:
no guideline followed
Principles of method if other than guideline:
The EU RAR summairses a number of non-Guideline studies
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material:
Sodium fluoride is water soluble and will rapidly dissociate under the aqueous conditions of the test to form sodium and fluoride ions. The toxicity of sodium fluoride is essentially due to fluoride ions and therefore is appropriate for read-across to KF.
Analytical monitoring:
not specified
Test organisms (species):
other: various
Test type:
static
Water media type:
freshwater
Remarks on exposure duration:
see details
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
83 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks on result:
other: Chlomonas paramaecium
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
101 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks on result:
other: Entosiphon sulcatum
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
180 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
other: inhibition of acid formation from glucose
Remarks on result:
other: Eschericia coli
Duration:
20 h
Dose descriptor:
NOEC
Effect conc.:
7.1 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks on result:
other: Uronema parduczi
Duration:
28 h
Dose descriptor:
NOEC
Effect conc.:
226 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
other: Inhibition of feed uptake
Remarks on result:
other: Microregma heterotoma
Duration:
16 h
Dose descriptor:
NOEC
Effect conc.:
231 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks on result:
other: Pseudomonas putida

The EU RAR reports NOEC values of between 7.1 -226 mg F/L.

Validity criteria fulfilled:
not specified
Conclusions:
NOEC values of between 7.1 -226 mg F/L are reported.
Executive summary:

The EU RAR summarises and reviews the available data on the toxicity of fluoride to aquatic microorganisms; NOEC values of between 7.1 -226 mg F/L are reported.

Endpoint:
activated sludge respiration inhibition testing
Remarks:
and other
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Dihydrogen hexafluorotitanate is an inorganic substance which will rapidly dissociate into fluoride, hydrogen and titanium ions upon dissolution in the environment. However, hydrogen and titanium ions do not remain as such in solution, only fluoride ions do. The approach follows scenario 1 of the RAAF (ECHA 2017).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source
sodium fluoride (CAS 7681-49-4)
Target
Dihydrogen hexafluorotitanate (CAS 17439-11-1)

3. ANALOGUE APPROACH JUSTIFICATION
The hydrogen ion attaches to a hydroxide ion to form a water molecule. The analysis of dissolved titanium levels in aquatic toxicity test solutions for algae, daphnia and fish according to OECD 201, 202 and 203 (Schlechtriem, 2013a, b; Teigeler, 2013) indicates that up to a loading of 100 mg/L dipotassium hexafluorotitanate, very low levels of titanium (often < 10% or even 5%) remain in solution at environmentally relevant pH while nearly all of the fluoride (often more than 95 %) could be recovered. Thus, regarding the environmental fate and toxicity of dihydrogen hexafluorotitanate, it can be assumed that toxicity (if any) will be driven by the fluoride anion. Therefore, full read-across to potassium fluoride (CAS #7789-23-3) and other fluorides based upon a molecular weight conversion is justified. The lowest available NOEC of 7.1 mg F/L results in a NOEC for microbial toxicity of 10.2 mg/L dihydrogen hexafluorotitanate.

4. DATA MATRIX
see attached read-across statement in section 13.2
Reason / purpose for cross-reference:
read-across source
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
83 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks on result:
other: Chlomonas paramaecium
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
101 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks on result:
other: Entosiphon sulcatum
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
180 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
other: inhibition of acid formation from glucose
Remarks on result:
other: Eschericia coli
Duration:
20 h
Dose descriptor:
NOEC
Effect conc.:
7.1 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks on result:
other: Uronema parduczi
Duration:
28 h
Dose descriptor:
NOEC
Effect conc.:
226 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
other: Inhibition of feed uptake
Remarks on result:
other: Microregma heterotoma
Duration:
16 h
Dose descriptor:
NOEC
Effect conc.:
231 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Remarks on result:
other: Pseudomonas putida

The EU RAR reports NOEC values of between 7.1 -226 mg F/L.

Validity criteria fulfilled:
not specified
Conclusions:
NOEC values of between 7.1 -226 mg F/L are reported.
Executive summary:

The EU RAR summarises and reviews the available data on the toxicity of fluoride to aquatic microorganisms; NOEC values of between 7.1 -226 mg F/L are reported.

Description of key information

Since dihydrogen hexafluorotitanate rapidly dissociates into fluoride, hydrogen and titanium ions upon dissolution in the environment, and only fluoride but not hydrogen and titanium ions will remain as such in solution, it can be assumed that toxicity (if any) will be driven by the fluoride anion. Therefore, full read-across of microbial toxicity data of potassium fluoride (CAS #7789-23-3) and other fluorides based upon a molecular weight conversion (and correction to max. purity) is justified (see below). The lowest available NOEC of 7.1 mg F/L for toxicity of fluoride to Uronema parduszi results in a NOEC for microbial toxicity of 16.74 mg/L dihydrogen hexafluorotitanate.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
16.74 mg/L

Additional information

Dihydrogen hexafluorotitanate


Since dihydrogen hexafluorotitanate rapidly dissociates into fluoride, hydrogen and titanium ions upon dissolution in the environment, and only fluoride but not hydrogen and titanium ions will remain as such in solution, it can be assumed that toxicity (if any) will be driven by the fluoride anion. Therefore, full read-across of microbial toxicity data of potassium fluoride (CAS #7789-23-3) and other fluorides based upon a molecular weight conversion (and correction to max. purity) is justified (see below). The lowest available NOEC of 7.1 mg F/L results in a NOEC for microbial toxicity of 16.74 mg/L dihydrogen hexafluorotitanate.


 


Sodium fluoride


The guideline-compliant Bayer study reports a 3 -hour NOEC of 510 mg/L for activated sludge. The EU RAR summarises and reviews the other available data on the toxicity of fluoride to aquatic microorganisms; NOEC values of between 7.1 - 226 mg/L are reported.